The present invention relates in general to timed alarm systems and in particular to improved apparatus for interdependent timing mechanisms that create a triggered before disarmed alarm system. Additionally, provision is made for automatic reset to standby after all input triggers are set to normal and a predetermined amount of time has transpired.
The present invention has as an important object the provision of an output source dependent upon a negative going input pulse or a positive going input pulse and a preset entry time delay; or a negative going input pulse without entry time delay function; all of which are interdependent upon the state of a disarm input and its associated exit delay function.
Another important object of the invention is to provide the interdependent timing functions using a minimum of component size and complexity with minimal quiescent (standby) current. This is accomplished by using CMOS integrated circuitry with appropriate supply filtering. The present invention requires only one hex-inverter integrated circuit which is the only active component excepting the output transistor. This is an important feature of the present invention.
It is a further object of the invention to achieve the foregoing objects with reliably operating apparatus yielding repeatable output indications and virtually insensitive to all but the most severe variations in the input supply.